title: Dynamic pH junction-sweeping for on-line focusing of dipeptides in capillary electrophoresis with laser-induced fluorescence detection.
abstract: In this paper, we developed a simple and effective on-line focusing technique combining dynamic pH junction and sweeping by capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection. Dynamic pH junction-sweeping is defined when the sample has a different buffer pH (dynamic pH junction condition) and is devoid of micelles (sweeping condition) relative to the background electrolyte (BGE). This hyphenated focusing mode was applied to the sensitive and selective focusing of four dipeptides: Tyr-Phe, Tyr-Leu, Trp-Gly, and Ala-Gln. Picomolar detectability of these dipeptides by CE-LIF detection was demonstrated through effective focusing of large sample volumes (up to 39% capillary length) using the dual pH junction-sweeping focusing mode. 25 mmol L(-1) sodium dihydrogen phosphate, pH 2.5 was used as the sample matrix, and 100 mmol L(-1) borate, 21 mmol L(-1) sodium dodecylsulfate (SDS), 16 mmol L(-1) Brij35, pH 9.0 as the background solution (BGS). The concentration detection limits (S/N = 3) of the four dipeptides were in the range of 1.0-5.0 pmol L(-1). The developed method has been successfully used for the determination of dipeptides in human serum samples.
authors.affiliation: Ministry of Education Key Laboratory of Analysis and Detection for Food Safety, Fujian Provincial Key Laboratory of Analysis and Detection for Food Safety, and Department of Chemistry, Fuzhou University, Fuzhou, Fujian 350002, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.forename: Lan
authors.initials: L
authors.lastname: Zhang
authors.forename: Zongwei
authors.initials: Z
authors.lastname: Cai
authors.forename: Guonan
authors.initials: G
authors.lastname: Chen
mesh_terms: D004151:Dipeptides / Q000032:analysis / Q000097:blood*; D019075:Electrophoresis, Capillary / Q000295:instrumentation* / Q000379:methods*; D005453:Fluorescence; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007834:Lasers; D057230:Limit of Detection; D012680:Sensitivity and Specificity
chemical_list: D004151:Dipeptides; C031703:tyrosylleucine; C016810:tryptophylglycine; C054122:alanylglutamine